The present invention is related to the field of cooling components on a printed circuit board. More specifically, the present invention is directed to an apparatus and method for providing improved heat transfer to a plurality of chips on a printed circuit board.
The ability to arrange electronic components on printed circuit boards having standard sizes allows for the easy configuration, assembly, repair and upgrading of electronic devices. Personal computers, for example, typically include a motherboard having multiple standardized ports or buses which include slots or connectors for attaching boards or cards. As a testament to the flexibility of this approach, connectors are included in nearly every personal computer, allowing for the addition of computer memory, connections to input/output (I/O) devices, and additional computing power.
Bus standards include, but are not limited, the Peripheral Component Interconnect (PCI) and the Industry Standard Architecture (ISA) standards, both of which have general utility, and the Accelerated Graphics Port (AGP) standard, which is designed for improving the graphics capabilities of computers. Each of these standards includes electrical and electronic standards for providing computational functions and mechanical standards to assure that the connectors and cards mate to provide the required electrical connections and physical stability. Of particular interest here are the mechanical standards, which include but are not limited to details of the geometrical configuration of the card edge that mates with the connector, the width, length and height of the assembled board, and the electrical specifications and power use of the card.
In addition to meeting the bus standards, it is important that card components including, but not limited to processors, memory chips, power supplies, and other electronic components, are operated within prescribed temperature limits. For high-power dissipating devices such as power supplies and processors, it is generally required that the operating temperature be kept below a maximum operating temperature. For boards having a plurality of temperature-sensitive components within the same circuit, maintaining individual chip temperatures within a range that allows all chips to operate the same. Thus, for example, memory chips often have temperature-dependent clock speeds. Circuits that have memory chips in parallel operate best if all the chips are within some temperature range, and thus have the same approximate clock speed.
Techniques for removing heat from electronic components has evolved with cooling demands. Fans of various types are used to force air out of the back of the enclosure or to force fresh air into the enclosure. In either case, such fans induce internal circulation and promote convective heat transfer from heat generating components. Other techniques include using more than one fan or ducting the flow within the enclosure to improve heat removal. On the component level, the use of passive heat sinks for heat removal from individual components is well known in the art. Axial fans or blowers are often added to high heat generating and temperature sensitive components, such as processors. These air moving devices increase the local heat transfer, moving thermal energy from one or several components into the enclosure. Techniques for improving heat sink contact with components have also been developed, as have active heat removal systems, such as heat pipes and Peltier devices.
The trend in recent years has been towards placing faster, more powerful computer chips having increased dissipation on each printed circuit board. These boards are normally stacked close to achieve a compact overall design. Stacking the boards may hinder the ability of the air to circulate near hot components, and may also reduce the effectiveness of chip or heat sink mounted fans or blowers. In addition, many high-end cards, such as GPUs, include a processor having a dedicated fan and other computer chips that should be operated at or near the same temperature. For example boards conforming to the AGP standard usually include a high power dissipating GPU and banks of clock-speed temperature-dependent memory chips, sometime laid out along two perpendicular lines about the GPU. Cooling systems thus need to cool the GPU to keep it from overheating and maintain a plurality of memory chips at or near the same temperature. The prior art methods are not sufficient to maintain several components, chips or sets of chips on one printed circuit board at or near a specified temperature. In addition, board standards require keeping all components within a specified height of the board so that adjacent slots can be used for other boards.
An example of a prior art problem and solution to a beat removal problem, as encountered in the design of an AGP board, is shown with reference to prior art FIGS. 1 and 2, which show the design specifications and component layout for an AGP card capable of consuming 50 Watts of power (a xe2x80x9cAGP Pro50xe2x80x9d card). The AGP Pro specification is being adopted to accommodate AGP-like cards that have greater power consumption and may require more space on the motherboard than does an AGP standard board. FIG. 1 shows an edge view of a motherboard 107 having an AGP Pro connector 109, a PCI card 110, and adjacent PCI connectors 111 and 113. AGP Pro connector 109 and PCI connectors 111 and 113 are parallel, are aligned with the length L of card 101, and are separated by a distance S. An AGP Pro compatible device 100 having a card 101 with a component side 115 and solder side 117 has a protruding portion 125 for electrically mating with connector 109, and a bracket 137 for fixing the AGP Pro compatible device to the computer frame (not shown). Bracket 137 is usually located near a wall of the computer enclosure and has an I/O connector mounted thereon (not shown) for making connections outside of the computer. An outline 103 specifies the maximum width W and height H of objects associated with component side 115, and an outline 105 specifies the maximum width W arid height B of objects associated with solder side 117. Of particular interest is outline 103. The original specifications for an AGP card call for an AGP compliant card to take up only the space between the AGP board and the next closest board (a height H less than S-B). Principally because of the increased power consumption, the original AGP standard was modified into an AGP Pro50 standard, which allows a card occupy a height H which overlaps the space of the adjoining PCI slots 111. The next closest position for inserting PCI card 110 is PCI connector 113, PCI cards that might have occupied PCI connector 111 are not available for use when AGP card 100 is in connector 109.
FIG. 2A shows a top view 2Axe2x80x942A of AGP card 100 from FIG. 1 showing various components to be cooled and a prior art method of cooling, and FIG. 2B shows a cross-sectional view of memory chips 121 and heat sink 131. Mounted on card 101 are a GPU 119 and a plurality of memory chips 121 arranged along two rows 129 and 131. Mounted on GPU 119 is a fan 135 for cooling the various components. Fan 135 is typically a vertical fan that draws air above card 100 as shown in FIG. 1 and towards GPU 100 to produce a vertical convective flow that subsequently flows over card 100 as shown by the arrows emanating from fan 135. Each of the rows 129 and 131 of memory chips 121 has a heat sink 123 placed on top of the memory chips and having fins that protrude away from card 100. As shown on FIG. 2B, heat sink 123 has a substantially flat bottom 126 that is in thermal contact with memory chips 121, and fins 124 that protrude away from the bottom. Heat sink 123 is of a material having a high thermal conductivity, usually a metal such as aluminum or copper. Fins 124 provide increased surface area for heat transfer, either through natural convection or by forced convection as shown by the flow of FIG. 1. While some portion of the flow from fan 135 is directed over heat sinks 123, the flow is generally diverging. This flow pattern has several adverse consequences, including having only a portion of the flow available to cool memory chips 121, providing uneven cooling between chips or along heat sink 123, and the possibility of allowing for flow separation or recirculation near the chips.
In general, the prior art solution to accommodate increased power dissipation is to increase the height H to allow for more circulation or for the inclusion of a larger fan or more advanced cooling devices. The AGP compatible device 100 thus becomes larger and overlaps with space that could otherwise be used by PCI cards. Unfortunately, increasing the board size or footprint is not an optimal method of accommodating increased power demands. Increasing the acceptable board size blocks access to adjacent slots, and thus reduces the computer""s capabilities and wastes wiring and connectors that already exist on the motherboard, and also results in a bulkier and possibly more expensive card.
What is needed is a method and/or apparatus that provides improved heat transfer characteristics for printed circuit boards. Specifically, there is a need to provide cooling to allow a plurality of computer chips to operate at approximately the same temperature within the confines of a computer enclosure. The operation of many types of computer chips is temperature sensitive, and the ability to cool a plurality of chips to approximately the same temperature allows for more reliable operation of the board. In particular, such a capability would allow for higher performance computer plug-in boards, such as graphics processors. In addition, there is a need to improve heat removal from boards so that boards having higher power dissipation can be cooled without increasing the amount of space taken up by the board within a computer enclosure.
The present invention provides an apparatus and method for cooling components within the confines of closely spaced printed circuit boards within an enclosure that allows for improved cooling. Specifically, the inventive cooling arrangement allows for enhanced and more accurate and predictable cooling of components on a computer board, thus allowing for higher performance of the board, such as operating at higher speed.
It is thus one aspect of the present invention to provide an apparatus and method for cooling a plurality of components on a computer board that maintains each of the components at a specified temperature or within a specified temperature range. In one embodiment, the cooling arrangement includes ducting to direct cooling flow from one or more fans along each of the computer chips. Embodiments for providing cooling flow include drawing air from a location internal to the computer enclosure and drawing in air external to the enclosures. Another embodiment provides cooling to a plug-in board adjacent an enclosure opening along the edge of the board, where the cooling air is ducted from an opening that falls within the height specification of a standard plug-in board. The chips may have heat sinks attached thereto, and the cooling flow may be directed along the heat sinks.
It is another aspect of the present invention to provide an apparatus and method for cooling components on a computer board by providing a housing for mounting one or more fans and elongated members such as fins or vanes to direct flow along the board and specifically along a plurality of components to be cooled. It is yet another aspect of the present invention to cool a plurality of electronic components by directing the flow over heat sinks attached to the plurality of electronic components. In one embodiment the plurality of components are arranged as two perpendicular array of components, and the flow is directed perpendicularly to the components, and a second embodiment arranges the plurality of components radially. The fans of the inventive cooling apparatus are alternatively placed on a heat sink that cools a high power consuming component, such as a GPU, while the flow is directed to cool a plurality of memory chips to within a given temperature range.
It is yet another aspect of the present invention to provide improved cooling to a standard sized computer plug-in board within a set height specification to allow for higher performance boards to occupy a defined physical space. In one embodiment, the inventive cooling system includes ducting to direct flow over heat sinks placed on arrays of computer components, such as memory chips, the cooling system including a heat sink with fans attached, elongated members for directing flow over the computer components, and a cover to further direct the flow.
It is another aspect of the present invention to cool a plug-in board while occupying less height over the board. One embodiment provides for cooling an AGP compatible plug-in board, including the GPU and memory chips, within the space confines of standard AGP height for large power consuming boards, such as boards consuming more than 50 watts of power. In one embodiment, a GPU has a heat sink attached that accepts a fan that draws in air away from the board and directs the flow towards memory chips that can cool each memory chip to within a specified temperature range within the width of regulation AGP board. The board may include one or more fans and may also include ducting to draw air in fresh cooling air from the point at which the AGP board meets a computer enclosure opening. It is yet another aspect of the present invention to provide cooling to components on computer boards using apparatus and methods have economic advantages by improving the performance or allowing for higher performance within the same amount of space within a computer.
A further understanding of the invention can be had from the detailed discussion of specific embodiments below. For purposes of clarity, this discussion refers to devices, methods, and concepts in terms of specific examples. However, the method of the present invention may operate with a wide variety of types of devices. It is therefore intended that the invention not be limited by the discussion of specific embodiments. For purposes of clarity, the invention is described in terms of systems that include many different innovative components and innovative combinations of components. No inference should be taken to limit the invention to combinations containing all of the innovative components listed in any illustrative embodiment in this specification.
Additional objects, advantages, aspects and features of the present invention will become apparent from the description of preferred embodiments, set forth below, which should be taken in conjunction with the accompanying drawings, a brief description of which follows.